php实现 str_replace替换指定次数的方法

<?php 
$str = &#39;abcdefgh&#39;; 
echo str_replace(&#39;abc&#39;, &#39;123&#39;, $str); // 123defgh  
$str = &#39;123456&#39;; 
$search = array(1, 2, 3, 4, 5, 6); 
$replace = array(&#39;a&#39;, &#39;b&#39;, &#39;c&#39;, &#39;d&#39;, &#39;f&#39;, &#39;g&#39;); 
echo str_replace($search, $replace, $str); // abcdefg  
$arr = array(&#39;abc&#39;,&#39;bac&#39;,&#39;cba&#39;); 
$result = str_replace(&#39;b&#39;, &#39;B&#39;, $arr, $count); 
print_r($result); // Array ( [0] => aBc [1] => Bac [2] => cBa ) 
echo $count;   // 3 共替换了3次 
?>

<?php 
$str = &#39;user_order_list&#39;; 
echo str_replace(&#39;_&#39;, &#39;/&#39;, $str); // user/order/list 
?>

<?php 
/** 
 * 对字符串执行指定次数替换 
 * @param Mixed $search  查找目标值 
 * @param Mixed $replace 替换值 
 * @param Mixed $subject 执行替换的字符串／数组 
 * @param Int  $limit  允许替换的次数，默认为-1，不限次数 
 * @return Mixed 
 */ 
function str_replace_limit($search, $replace, $subject, $limit=-1){ 
  if(is_array($search)){ 
    foreach($search as $k=>$v){ 
      $search[$k] = &#39;`&#39;. preg_quote($search[$k], &#39;`&#39;). &#39;`&#39;; 
    } 
  }else{ 
    $search = &#39;`&#39;. preg_quote($search, &#39;`&#39;). &#39;`&#39;; 
  } 
  return preg_replace($search, $replace, $subject, $limit); 
} 
?>

<?php 
$str = &#39;user_order_list&#39;; 
echo str_replace_limit(&#39;_&#39;, &#39;/&#39;, $str, 1); // user/order_list  
$arr = array(&#39;abbc&#39;,&#39;bbac&#39;,&#39;cbba&#39;); 
$result = str_replace_limit(&#39;b&#39;, &#39;B&#39;, $arr, 1); 
print_r($result); // Array ( [0] => aBbc [1] => Bbac [2] => cBba ) 
?>